It is already known to provide a plurality of discrete antennas such as e.g. dipole antennas in a spatially distributed fashion, e.g. along a tunnel structure or in other buildings to provide suitable radio coverage within the whole structure. Further, it is also known to provide coaxial radiating cables for RF supply within confined spaces, which provide coverage along the cable.
However, deploying a plurality of discrete antennas is very costly due to the requirements of individual mechanical and electrical installation of each discrete antenna and the like, and the coaxial radiating cable has the significant disadvantage of increased attenuation at higher frequencies, e.g. in the GHz range.
Generally, coaxial cable can be operated only up to the so-called cut-off frequency which is a function of the cable diameter. The frequency range supported by this cable is a very important characteristic. The higher the operational frequency is the smaller the coaxial cable has to be. At the same time the attenuation increases with decreasing diameter and increasing frequency. Especially the relatively high attenuation incapacitates coaxial radiating cable to provide RF coverage at frequencies above 4 GHz in long distance systems like tunnels. Repeaters have to be installed in very short distance.
Thus, it is an object of the present invention to provide an improved distributed antenna system and a method of manufacturing such system which avoid the aforementioned disadvantages of the prior art systems.